Spark plug broke - parts in motor

[trowa]

01 Mitsubishi Eclipse - 4cyl - 78,000 miles - automatic

I was driving at highway speeds when I felt my car shudder and the "Service Engine" light lit up. The car continued to shake, becoming worse while stopped at stoplights.

I had it towed to the mechanic, where they determined that the ground electrode (L-shaped bracket) at the bottom of a spark plug had corroded/fallen off, and also the round tip had fallen in the engine. A compression test expelled nothing, so they had to open up the engine and find the broken-off parts. This was an expensive repair, and I would like to know who to blame (if anyone)

Two notes:

1. I had taken the car in about a month ago to have the timing belt replaced at 76,000 miles. Could a this have contributed to the problem? (i.e. overheating/bad timing because of a poor installation)

2. My last tune-up (replaced plugs) was in Sept 2003 at 45,000 miles. No problems until this.


Thanks!

[DanD]

I can’t say for sure but if the car ran normally for 2000 miles I don’t think the timing belt job would be at fault.
If the engine were mistimed you would have felt that the engine was not running properly as soon as you drove it off their lot.
Even if the belt had jumped there is a much larger chance of a valve becoming bent then the spark plug being damaged.
Why a spark plug would do this (age and mileage?) is a bit of a mystery but it’s a piece of the machinery and anything can happen.
Does the spark plug look like it was hit or are just the electrodes missing?
Dan.

[trowa]

It appears that the electrode broke off fairly neatly, taking with it a small round donut-like piece (pardon my ignorance of the part in question) I don't see any other damage to the plug.

Thank you for your reply.

[DanD]

The only thing I can think of other then a defective spark plug, is that maybe the engine were detonating but you would have heard the spark knock or severe pinging on acceleration.
As you didn’t mention anything like that I assume that you didn’t hear any, again pointing to a defective plug.
Very unfortunate but I can’t lay any blame for this, not even towards you 33.000 miles is not out of line for a spark plug with today’s cars.
Dan.